Spaghetti is terrible for dogs.
Chocolate is terrible for dogs. Ham is not good either.
But I never heard that spaghetti is not good for dogs, unless you simply mean “too much spaghetti”.
I don’t see “Spaghetti” listed here: Things That Are Dangerous For Dogs http://terra4incognita.wordpress.com/2007/05/10/things-that-are-dangerous-for-dogs/
From no less an authority on all things natural - motherearthliving.com:
Doggie Dinner: Spaghetti with Meat Sauce
8 ounces whole-wheat spaghetti, cooked and drained
1 pound hamburger, fried
4 medium mushrooms, cut into pieces
1 medium tomato, chopped
½ cup tomato juice
Mix hamburger with mushrooms, celery and chopped tomato. Stir in tomato juice. Pour over spaghetti and serve warm.
Give ‘em whole-wheat spaghetti.